This invention relates to a semiconductor laser and a method of producing the same which has recently rapidly extended its application to light sources for various types of electronic equipment and optical apparatus and is now greatly in demand.
One of the important functions of a semiconductor laser which is required when it is used as a coherent light source for electronic equipment or optical apparatus is oscillation at a single spot, or single transversal mode oscillation. To realize this, it is necessary to suppress the spread of laser light and confine the light by a concentration current flowing through the laser element near the active region in which the laser light propagates. This type of semiconductor laser is normally called the stripe-type semiconductor laser.
A relatively simple method for the stripe type is to only restrict current to be narrow. The laser according to this method needs a high threshold value for realization of the single transversal mode oscillation. The stripe type which can oscillate at the lowest threshold is a buried stripe type semiconductor laser (normally called the BH laser). The production of this type of laser, however, requires that the crystal growth process be performed twice whereas with other lasers this process need normally be performed only once, that is, it is necessary that after the multilayered films including an active layer are grown the buried region be removed and then a buried layer be again grown. In addition, it is somewhat technically difficult to produce this laser.
It is an object of this invention to provide a method of producing a semiconductor laser in which the buried-stripe structure that is necessary to oscillate in a single transversal mode at a low threshold value can be produced by a single crystal growth process.